Simple introductory Powerpoint

1. Properties of Covalent Substances,
Metals, and Ionic Compounds

2. Molecular substances have a broad range
of physical and chemical properties.
• Gases are elements such as Noble gases or
diatomic nonmetals (N2 , Cl2 , H2 , O2 , F2)
or small, nonpolar compounds. Weak
intermolecular forces do not let molecules stick
to one another to form liquids or solids.
• Liquids are molecular compounds with
intermediate-strength intermolecular forces.
Molecules are slightly polar. They stick together
but not in rigid structures.

3. • Solids are of 4 major types:
1) Ionic compounds – positive & negative ions
arranged in repeating patterns. SALTS!!!!
Held together very strongly in 1 big structure
called a crystal lattice.
Hard, brittle solids with high melting points.
Many are soluble in water because water is
polar.
NO MOLECULES!
Lots more info later! 

4. 2) Covalent network crystals - no separate
molecules. Atoms are bonded to all
surrounding atoms with covalent bonds.
Very hard & brittle, insoluble in water.
Diamond, graphite and quartz are examples.

5. Metallic solids – layers of metal atoms that all
share a “sea of valence electrons”.
 Valence electrons move FREELY between layers
of atoms. These delocalized electrons cause
metallic properties, especially electrical
conductivity.
 amounts of energy can be absorbed and
Very small
released by these
electrons:
this makes metals…
shiny!

6. Metallic Properties
Bonds are ALWAYS occurs between METAL atoms (Triple
DUH!)
Malleability – can be hammered into shapes
Luster –shiny!
Ductility – can be stretched into a wire
Metals have a broad range of melting points, good
conductors of heat &
electricity.

7. 4) Covalent molecular compounds – made of
individual molecules. (molecules are groups of
atoms held together by covalent bonds with
specific numbers of atoms and in specific
geometric arrangements)
Properties vary broadly depending on how
POLAR the molecules are.
INTERMOLECULAR FORCES hold molecules
near one another. The strength of these forces
determines the physical properties of the
substance.
London dispersion <dipole-dipole< hydrogen bond

8. Very special Properties of
1. 104.5o bond angle
WATER
2. 2 unshared pairs of valence electrons on oxygen atom
3. Strongly polar covalent bond between O and H
Hydrogen bonding between water molecules

9. • Surface tension – all particles of a liquid are attracted
to one another (COHESION), but particles at the
SURFACE of the liquid only have other particles of the
liquid underneath them. This produces uneven
attractions that pull surface particles closer together
than particles within the body of the liquid.

10. • Capillary action – particles of the liquid are attracted to
particles of their container (ADHESION). This causes
the liquid to be pulled up into a narrow tube higher
than if only gravity were acting. Allows water to rise in
plant stems and blood to move into glass capillary
tubes.

11. Why does ice float?
When water molecules cool,
their movement slows and
more hydrogen bonds can
form. Molecules are forced
into a more rigid pattern that
spreads them farther apart
than in liquid phase.
When molecules are farther
apart, there are fewer
molecules in a unit of volume
and the density is less. Ice is
LESS DENSE than water!

12. Ionic vs. Molecular
Compounds
Forces BETWEEN ions Forces WITHIN molecules
are very strong. are very strong. Forces
HIGH melting & boiling BETWEEN molecules are
points; hard, brittle much weaker.
solids. LOWER m.p. & b.p.,
Solids DO NOT conduct softer solids, liquids or
electricity; fixed charges gases.
AQUEOUS solutions Do not conduct electricity.
do conduct; mobile
charges.
“aqueous” means
“dissolved in water”

13. Ionic Compound Vocab
FORMULA UNIT: Simplest collection of atoms
in an ionic compound
Expressed as an EMPIRICAL FORMULA:
smallest whole number ratio of elements
THERE ARE NO MOLECULES in an ionic
compound.
CRYSTAL STRUCTURE: all ions surrounded
by ions of opposite charge.

14. Examples of Crystal Structures:
NaCl and CaF2